XPS study on the Bi-2212 single crystals grown by a modified vertical Bridgman method

We carried out surface cleaning of Bi2Sr2CaCu2Oy (Bi-2212) single crystals grown by a modified vertical Bridgman method (modified VB method), and investigated the chemical state with X-ray photoelectron spectroscopy. From the results, we found that carbon impurities on the surface of the single crystals were mostly removed by cleaving them in the high vacuum (7.3×10−6 Pa). The O-1s peak from the cleaved surface of the single crystal was very sharp and its FWHM value was about 2.0 eV. Moreover, we knew that the crystals did not include any carbon impurities, and that they had few mutual substitutions between Ca and Sr. Therefore, the single crystals grown by a modified VB method is expected to have a high quality.